The present invention relates to an apparatus for releasing a drive assembly from a driven member and connecting the same thereto, more particularly to an apparatus by which the coupling member of a drive assembly including a universal joint, ball joint, gear coupling or the like can be released from and connected to a driven member and which is especially useful for drive assemblies interconnecting the rolls of rolling mills to drive means.
Generally, working rolls of rolling mills are replaced with the use of a crane by which the roll is moved as suspended therefrom, or with the use of hydraulic means. In the former method, a C-shaped hook or porter bar is usually used. In recent years, a pair of upper and lower rolls are released from or connected to the driven shafts at the same time with the use of a double-eye C-shaped hook or porter bar in order to shorten the work time.
When the pair of upper and lower working rolls are handled at the same time, the coupling members of the upper and lower universal joints for the necks of the upper and lower rolls must be held at the same center-to-center spacing as the upper and lower rolls, whereas it is extremely difficult to maintain the upper and lower rolls at definite levels especially when a crane is used.
It is further noted that torque transmission between the coupling and the roll neck is effected through a joint including a key or a portion of oval rectangular cross section fitting in a bore of corresponding shape. If there is a relative angular displacement between the coupling and the roll to be joined thereto, it is extremely difficult to eliminate such angular displacement to fit them together, because the roll neck is supported by a C-hook or porter bar and is not rotatable.
Because of these difficulties, the insertion of the roll neck into the coupling gives a high impact load to the drive assembly, permitting the roll neck to strike the coupling when the corresponding portions to be joined together differ greatly in the above-mentioned spacing or involve a great angular displacement.
Japanese patent application published as Publication No. 4767/1966 proposes a method of releasing a roll of rolling mill from a spindle by moving the spindle or its coupling toward the drive means from the roll. According to the proposed method, a gear-type coupling interconnecting the roll neck to the spindle has a boss (intermediate shaft) joined to the spindle and supported by a bearing at all times. The bearing is rotatably and vertically slidably mounted on an upright post on a frame which is equipped with a support for supporting the outer tube of the coupling. The outer tube on the support is vertically shiftable for adjustment, and the spindle is rotatable. The other boss of the coupling joined to the roll neck is releasable from and connectible to the roll neck by the axial movement of the frame.
Generally with rolling mills, the roll neck and the coupling, although fitted together with a loose fit, are designed to involve the least possible backlash, so that very high pressure usually acts between the outer surface of the roll neck and the inner surface of the coupling as if in a press fit. Accordingly, with the rolling mill disclosed in the foregoing publication, the holding force acting between the outer surface of the roll neck and the inner surface of the boss of the coupling joined to the roll neck is sometimes greater than the frictional force between the outer tube of the coupling and the support when the frame is axially moved to release the coupling from the roll neck, because the outer tube of the coupling merely bears on the support positioned thereunder. Consequently, the support idly slides on the outer tube of the coupling by a distance corresponding to the axial backlash inherently involved in the coupling, frequently failing to smoothly remove the coupling from the roll neck for the replacement of the roll.
Further since the roll neck fits in the boss of the coupling joined thereto as by a press fit, the above-mentioned axial movement of the frame first expands spring provided in the coupling by a length corresponding to the axial backlash of the coupling, axially moving only the other boss (intermediate shaft) joined to the spindle. Subsequently, the boss of the coupling joined to the roll neck is separated therefrom, abruptly moving toward the spindle simultaneously with the contraction of the spring. This produces an impact within the coupling, possibly causing damage to the coupling.
Additionally, since the outer tube of the coupling is supported by the support at two points, there is difficulty in supporting the coupling in balance, with the result that the boss to be joined to the neck of a new roll is liable to be positioned at a lower level than is desired. If the coupling is thus out of alignment with the roll, the boss will strike the roll neck, failing to fit around the neck of the roll to be substituted. It is further noted that the bearing for supporting the boss of the gear-type coupling joined to the spindle serves as a so-called carrier, so that it rotates with that boss in contact therewith at all times, thus entailing a great power transmission loss.
With rolling mills, the upper and lower working rolls are replaced with the upper roll placed on the lower roll in intimate contact therewith. When new upper and lower working rolls are intalled on the lower backup roll, the center of the new lower working roll has been shifted from the center of the old lower working roll by an amount corresponding to 1/2 the difference in diameter between the new and old working rolls. The distance between the centers of the new upper and lower working rolls is greater than like distance between the old upper and lower working rolls by the sum of the difference in radius between the new and old upper working rolls and the difference in radius between the new and old lower working rolls. Generally, the upper and lower working rolls used in a pair are approximately equal in diameter. Based on the top surface of the lower backup roll, therefore, the center of the new lower working roll mounted in place has been vertically shifted from that of the old lower working roll by 1/2 the difference in diameter between the new and old lower working rolls. Similarly, the center of the new upper working roll has been vertically shifted from that of the old upper working roll by 3/2 times the difference in diameter between the new and old upper working rolls. The replacement of the working rolls involves such a definite relationship. However conventional roll replacing apparatus are not provided with means for aligning new upper and lower working rolls with corresponding couplings respectively in accordance with this relationship and therefore involve great difficulties in replacing the working rolls.